I read in the brochure that the frame is made in three different sections, each out of a different type of steel. I talked to the people at Toyota to find out more about it. They said, “The frame design allows us to provide the right amount of strength and rigidity at each area of the truck. The front section from behind the bumper to the front of the cab is fully boxed steel. This is done to provide a crumple zone area for frontal impact energy management as well as to manage the torsional forces put out by the engine and transmission.
“The second section runs under the cab area to near the forward rear spring mount. This area is a rolled lip c-channel steel design that has reinforcements at key locations. This section is set up to absorb side impact energy and to provide a comfortable ride for the occupants in the cab. Some frame flexing in the cab area improves overall ride quality.
“The third section runs under the majority of the bed area. It is an open c-channel design that incorporates a bit more frame flexing. This works well with the rear leaf spring suspension to support heavy loads, while providing excellent ride quality in the cab area. This is the sort of frame design one finds on heavy-duty trucks and semi tractors.”